Influence of calcium on the uptake of ingested strontium

Radioactive isotopes of strontium, mainly 90Sr, released into the environment due to nuclear accidents may contribute significantly to the internal radiation exposure of members of the public after ingestion of strontium with contaminated foodstuffs. The committed radiation dose is significantly dependent on the fraction of the ingested activity that crossed the gut wall (f1 value). The directive 96/29/EURATOM has adopted f1 values of 0.3 for adults. This study was aimed to investigate how far the calcium content of foodstuffs influences the uptake of ingested strontium. For aqueous solutions without calcium containing 1 mg strontium, f1 values of 0.62±0.13 (mean±SD) were obtained. However, the uptake of 1 mg Sr from milk, and respectively from solutions with calcium was lower than from aqueous solution (f1:=0.32±0.06, respectively f1:=0.31±0.06). The data obtained show a significant reduction of the uptake of ingested strontium from milk in comparison to aqueous solution. The calcium content of milk could explain this reduction. (orig.)